WO2024258880A2

WO2024258880A2 - Hip trajectory error framework prosthetic feet for above-knee prosthetic legs

Info

Publication number: WO2024258880A2
Application number: PCT/US2024/033459
Authority: WO
Inventors: Nina T. PETELINA; V Amos Greene Winter
Original assignee: Massachusetts Institute of Technology
Current assignee: Massachusetts Institute of Technology
Priority date: 2023-06-12
Filing date: 2024-06-11
Publication date: 2024-12-19
Anticipated expiration: 2025-12-12
Also published as: WO2024258880A3

Abstract

Methods for designing a prosthetic feet for use by above-knee amputees, and the resulting prosthetic foot designs, are disclosed. The prosthetic foot can be optimized to best replicate hip movement of an able-bodied user for an above-knee amputee that inherently lacks early and mid-stance knee flexion. The replication can be determined by minimizing what is referred to as a hip trajectory error. The resulting prosthetic foot design includes a keel, an elongated forefoot section attached to the keel at an attachment point, the forefoot section having a toe portion anterior to the attachment point, and a heel attached to the forefoot section and positioned posterior to the attachment point. The keel, the forefoot section, and the heel are configured to provide both shock absorption and replication of hip motion of a comparable able-bodied user despite a lack of early-stance knee flexion and mid-stance knee flexion to an above-knee amputee.

Description

HIP TRAJECTORY ERROR FRAMEWORK PROSTHETIC FEET FOR ABOVEKNEE PROSTHETIC LEGS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims benefit of priority from a U.S. Provisional Application No. 63/507,478, filed June 12, 2023, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD

[0002] The present application relates to devices and methods for manufacturing devices for use as prosthetic feet, and more particularly relates to devices and methods for manufacturing devices that can be used as prosthetic feet by individuals with above-knee amputations and that can replicate close to normal hip center motion when used by such individuals.

BACKGROUND

[0003] Many amputees lack access to high-performance prosthetic feet because it is difficult to find a good fit of a high-performance prosthetic foot for people with a lower limb amputation. However, availability of such prosthetics can greatly improve their mobility and quality of life. Access to certified prosthetists is limited, thereby limiting the time and resources available for the fitting process. Furthermore, at least because the relationship between the mechanical function of prosthetic feet and user outcomes is not yet fully understood, prostheses are often designed using extensive user testing and iterative design methods. This design method can be costly, and can limit the development of prosthetic devices. As a result, often prosthetic feet are designed for the most common amputee demographics in high income countries, thus excluding people outside the average population of prosthetic foot users.

[0004] Numerous studies have shown that mechanical design of a passive prosthetic foot can affect a user's gait. Several metrics are available for assessing the quality and/or the functionality of a passive prosthetic foot. For example, roll-over geometry, which is defined as a path of a center of pressure during stance phase, as measured in an ankle-knee reference frame, is used to assess a prosthetic foot. Roll-over geometry offers advantages over other metrics because it can be evaluated under physiological walking conditions, providing a target design or shape without inherent variability associated with human subjects. However, because roll-over geometry is measured in an ankle -knee reference frame, without including any information regarding the orientation of the ankle-knee reference frame relative to the global reference frame, it is possible that two different prosthetic feet have identical roll-over geometries and yet exhibit very different lower leg kinematics during gait. Therefore, rollover geometry is insufficient as a design parameter in at least some instances.

[0005] The lower leg trajectory error (LLTE) quantifies how closely the position of the lower leg segment of a given prosthetic foot is able to replicate a target physiological lower leg position throughout the course of a step. LLTE can be used for calculating the shape and size of a passive prosthetic foot for a below-knee amputee. However, prosthetics based on LLTE are generally large, heavy and include relatively complex mechanisms and fails to generate functional prosthetics for above-knee amputees. Prosthetic for individuals with above-knee amputation should incorporate the functionality lost due to the lack of early and mid-stance knee flexion during a user’s gait cycle. Prosthetic for individuals with aboveknee amputation should promote user mobility, shock absoiption, and be amenable to be designed based on clinical and/or user guidelines such as ambulation level and/or needs.

[0006] Accordingly, there is a need to develop devices, systems, and methods that enable quantitative and predict design of lower limb prosthesis for above -knee amputees while also minimizing the cost and fitting time associated with the design and manufacture of such prosthesis.

SUMMARY

[0007] The present disclosure is generally directed to various embodiments of prosthetic feet that can be used by above-knee amputees. The prosthetic foot described in this disclosure includes a keel attached to a forefoot portion at an attachment point. The forefoot portion is positioned anterior to the attachment point and a heel positioned posterior to the attachment point. The heel is configured to be flexible so as to provide shock absorption when the heel strikes the ground. Such a prosthetic foot can be defined by a parametric curve comprising a set of coefficients (e.g., Bezier coefficients) and identifying a set of determinants that are used to minimize a hip trajectory error (HTE). The HTE is calculated under reference loading conditions and the identified set of determinants are optimized by minimizing the HTE relative to a target kinetic and kinematic data. The target kinematic and/or kinetic data set may be based on body size and/or the weight of the user or an able- bodied individual, and/or other factors provided for herein or otherwise appreciated by those skilled in the art in view of the present disclosures. The prosthetic foot can be fabricated based on the optimized design of the prosthetic foot.

[0008] One exemplary embodiment includes a prosthetic foot for use with an above -knee amputee. The prosthetic foot includes a generally vertical keel, a generally horizontal elongated forefoot section, and a heel. The elongated forefoot section is attached to the keel at an attachment point, while the forefoot section has a toe portion anterior to the attachment point. The heel is attached to the forefoot section and is positioned posterior to the attachment point. The keel, the forefoot section, and the heel are configured to provide for a user who is an above-knee amputee both shock absorption and replication of hip motion of a comparable able-bodied user despite a lack of early-stance knee flexion and mid-stance knee flexion due to the user being an above -knee amputee.

[0009] In at least some embodiments, the keel and the forefoot section of the prosthetic foot can be configured to be positioned at an angle of about 45 degrees to about 75 degrees with respect to each other. The heel of the prosthetic foot can be at least 50% longer than the toe portion in length. In some embodiments, the heel of the prosthetic foot can be configured to deform under pressure and provide shock absorption when the heel strikes the ground. In at least some embodiments, the keel and the forefoot section can be shaped according to a parametric curve characterized by one or more determinants selected from a group including h, Cid, C?x, Ciy, C2d, Cdx, Cay, Csd, Cdx, Cdd, Csd, C&d, and C?d-

[0010] The prosthetic foot can be optimized based on at least one of the user's body weight, height, foot size, limb length, and/or walking pattern. In some embodiments, the prosthetic foot can optimized based on at least two of those parameters, and in some other embodiments, the prosthetic foot can be optimized based on at least three of those parameters.

[0011] The keel and the forefoot section can be shaped to minimize a hip trajectory error (HTE). In at least some such embodiments, the action of determining the HTE can include calculating an HTE score based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user. The HTE score can be further based on leg length from floor to hip center of the above-knee amputee using the prosthetic foot and number of stance frames used for optimization. In some embodiments, the HTE score can be approximately in the range of about 0.01 to about 0.025.

[0012] In at least some embodiments, the hip motion of the above-knee amputee using the prosthetic foot can be approximately in the range of about 3% of the hip motion of the able- bodied user to about 20% of the hip motion of the able-bodied user. In at least some embodiments, the prosthetic foot can comprise at least one of nylon 6/6, carbon fiber, fiber glass, spring steel, titanium, plastic, an alloy of metals, a polymer, a composite, a resin, a thermoplastic, laminate, a rubber, an elastomer, a non-viscoelastic material, a viscoelastic material, and/or wood.

[0013] One exemplary embodiment of a method of designing a compliant prosthetic foot includes using a compliant mechanism optimization technique that includes a set of determinants for the compliant prosthetic foot, calculating a hip trajectory error (HTE) under at least one reference loading condition, optimizing the set of determinants by minimizing the hip trajectory error relative to a target kinematic data set, and designing the compliant prosthetic foot based on the optimized set of determinants.

[0014] In at least some embodiments, the method can further include fabricating the compliant prosthetic foot based on the optimized set of determinants. The prosthetic foot can include a generally vertical keel, a generally horizontal elongated forefoot section, and a heel. The elongated forefoot section can be attached to the keel at an attachment point, and the heel can be attached to the forefoot section and positioned posterior to the attachment point.

[0015] The set of determinants can include one or more determinants selected from h, Cid, Cix, C2y, C2d, Csx, C _y, C3d, C4X, Cdd, Csd, Cftd, and C?d- The optimized set of determinants can be based on at least one of the user's body weight, height, foot size, limb length, and/or walking pattern. The target kinematic data set can include a physiological data set of a user. In some such embodiments in which the target kinematic data set includes include a physiological data set of a user, and the physiological data set can be obtained from an able- bodied subject with about the same body size and mass as the user. In some embodiments, the physiological data set can be scaled from an able-bodied subject to adjust for differences in body size and mass compared to the user. [0016] In some embodiments of the method, the step of determining the hip trajectory error (HTE) can comprise calculating an HTE score based on predicted hip motion of the aboveknee amputee using the prosthetic foot and hip motion of the able-bodied user. In some such embodiments, calculating the HTE score can be further based on leg length from floor to hip center of the above-knee amputee using the prosthetic foot and number of stance frames used for optimization. The HTE score can be approximately in the range of about 0.01 to about 0.025.

[0017] In some embodiments of the method, the compliant mechanism optimization technique can include a parameterization step in which wide Bezier curve coefficient can be incorporated into a genetic algorithm to determine a set of determinants that minimizes a hip trajectory error of the prosthetic foot. The compliant mechanism optimization technique can include a parameterization step in which polynomial interpolation curve parameters can be incorporated into a genetic algorithm to determine a set of determinants that minimizes a hip trajectory error of the prosthetic foot. In at least some embodiments, the compliant mechanism optimization technique can include a parameterization step in which Lagrange function curve parameters can be incorporated into a genetic algorithm to determine a set of determinants that minimizes a hip trajectory error of the prosthetic foot. In any of these embodiments, the method can further include combining the compliant mechanism optimization technique with the hip trajectory error and identifying prosthetic foot design parameters that do not exceed a predefined design space.

[0018] The prosthetic foot can be fabricated by at least one of machining, three- dimensional printing, implementing a layup method, implementing a waterjet method, additive fabrication, subtractive fabrication, lamination, composite manufacture, injection molding, carbon fiber fabrication, extrusion, casting, molding, co-molding, carving, and/or vulcanization.

[0019] One exemplary embodiment of a method of moving by an above-knee amputee having a prosthetic foot includes moving a leg that is amputated above the knee and includes a prosthetic foot in a manner such that resulting hip motion of the above-knee amputee substantially replicates hip motion of a comparable able-bodied user.

[0020] In at least some embodiments of the method of moving, the hip motion of the above-knee amputee using the prosthetic foot can be approximately in a range of about 3% of the hip motion of the able-bodied user to about 20% of the hip motion of the able-bodied user.

[0021] The prosthetic foot involved in the method can include e a generally vertical keel, a generally horizontal elongated forefoot section, and a heel. The elongated forefoot section can be attached to the keel at an attachment point, the forefoot section can have a toe portion anterior to the attachment point, and a heel can be attached to the forefoot section and can be positioned posterior to the attachment point. The keel, the forefoot section, and the heel can provide shock absorption when the above-knee amputee is moving. The prosthetic foot can be designed based on one or more determinants optimized to minimize a hip trajectory error (HTE) relative to a target kinematic data set. In some embodiments, the HTE can be based on a predicted hip motion of the above -knee amputee using the prosthetic foot and hip motion of the able-bodied user. In at least some embodiments, the HTE can be based on leg length from floor to hip center of the above-knee amputee using the prosthetic foot and number of stance frames used for optimization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] This disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1 is a perspective view of one embodiment of a prosthetic foot of the prior art for use by an above-knee amputee;

[0024] FIG. 2 is a schematic side view of a hip center trajectory, locked knee stance of an above-knee amputee and an early stance knee flexion of an able-bodied individual;

[0025] FIG. 3A is a perspective view of one embodiment of a prosthetic foot of the present disclosure, the foot including a vertical heel attached to a forefoot section at an attachment point;

[0026] FIG. 3B is a side perspective view of the prosthetic foot of FIG. 3A;

[0027] FIG. 3C is a top perspective view of the prosthetic foot of FIG. 3A;

[0028] FIG. 3D is a side view of the prosthetic foot of FIG. 3A; [0029] FIG. 4 is a schematic side view of a parametric model for a Hip Trajectory Error (HTE) foot prototype defined using Bezier curve coefficients;

[0030] FIG. 5 is an illustration of one embodiment of the prosthetic foot according to this disclosure as used by an above-knee amputee;

[0031] FIG. 6A is a schematic side view of a target able-bodied motion through an early stance phase and a mid-stance phase;

[0032] FIG. 6B is a schematic side view of a predicted performance for an LLTE-objective prosthetic foot and an HTE-objective prosthetic feet, indicating respective HTE scores; and

[0033] FIG. 6C is a schematic side view of a performance of the LLTE-objective prosthetic foot and the HTE-objective prosthetic feet at maximum knee flexion during an early stance phase and a mid-stance stance phase for an able-bodied gait as identified on a graph illustrating typical gait cycle.

DETAILED DESCRIPTION

[0034] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are nonlimiting exemplary embodiments and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure.

Accordingly, aspects and features of every embodiment may not be described with respect to each embodiment, but those aspects and features are applicable to the various embodiments unless statements or understandings are to the contrary.

[0035] The figures provided herein are not necessarily to scale, although a person skilled in the art will recognize instances where the figures are to scale and/or what a typical size is when the drawings are not to scale. While in some embodiments movement of one component is described with respect to another, a person skilled in the art will recognize that other movements are possible. Additionally, a number of terms may be used throughout the disclosure interchangeably but will be understood by a person skilled in the art. By way of non-limiting example, the terms “prosthetic foot,’’ “prosthesis,’’ and “foot” may be used interchangeably with one another. By way of further non-limiting example, the terms “user” and “amputee” may be used interchangeably with one another.

[0036] Additionally, the following terms shall have the following definitions, unless otherwise indicated. A “compliant mechanism optimization technique” is a means of searching for, identifying, and designing a structure for a targeted deflection under a given load. A genetic algorithm, or other optimization technique, may be used to determine the optimized set of determinants. A “compliant prosthetic foot” or a “compliant structure” is a prosthetic foot that deforms under load. A “reference loading condition” is a targeted or anticipated loading that a foot could experience. An “optimized set of determinants” is a set of variables describing size, form, shape, material, and structure of a prosthetic foot in a configuration to provide a targeted deflection under a given load.

[0037] Further, to the extent features, sides, or steps are described as being “first” or “second,” such numerical ordering is generally arbitrary, and thus such numbering can be interchangeable. Still further, in the present disclosure, like-numbered components of various embodiments generally have similar features when those components are of a similar nature and/or serve a similar purpose. Still further, the present disclosure includes some illustrations and descriptions that include prototypes or bench models. A person skilled in the art will recognize how to rely upon the present disclosure to integrate the techniques, systems, devices, and methods provided for into a product in view of the present disclosures.

[0038] The present disclosure relates to systems, devices, and methods of manufacturing prosthesis for above-knee amputees. More particularly, embodiments of a prosthetic foot are disclosed herein that are designed based on a specific user’s body weight, foot size, height, limb lengths, and/or preferred walking pattern. In other words, the present disclosure provides systems, methods, and prosthesis that are optimized for individual users and that can aid improving the gait of above-knee amputees. This is because the present disclosure allows for prosthetic feet that allow for a more natural hip motion for the user.

[0039] As discussed in detail herein, a prosthetic foot optimized to minimize hip trajectory error can be used by above-knee amputees lacking early and mid-stance knee flexion. Such a prosthetic foot can replicate able-bodied loading (center of pressure (CoP) and ground reaction force (GRF) progression) to enable predictable knee mechanism operation. A Hip Trajectory Error (HTE) framework is used for quantitatively and predictively designing such low-cost, high biomechanical performance prosthetic feet for people with an above-knee amputations. A person skilled in the art will appreciate other embodiments of the prosthetic feet and methods of designing such prosthetic feet beyond those disclosed herein and/or are otherwise derivable from the present disclosures.

[0040] FIG. 1 is a typical prosthetic foot 10 found in the prior art. The prosthetic foot 10 is configured to be used with a prosthetic knee 2 to aid an above-knee amputee in walking.

FIG. 2 illustrates limb motion based on the movement of a person’s hip 6, knee 8, and ankle 12 for an above-knee amputee and an able-bodied person. Unlike below -knee amputees, above-knee amputees use prosthetic feet 10 that have to account for a lack of knee flexion. As shown in FIG. 2, above-knee amputees typically have a locked knee stance 14 and cannot replicate able-bodied motion because most commercial above-knee prosthesis do not provide early stance knee flexion 16 that able-bodied individuals have as a result of a physiologically functioning knee 8. The main functions of early and mid-stance as a result of the knee flexion are shock absorption, progression, and stability. The lack of proper shock absorption can affect a hip center trajectory 18 when the user is walking and can, in turn, lead to visible compensatory behaviors and secondary health issues to the hip joint, residual limb, and the lower back of an above-knee prosthesis user. Therefore, above-knee amputees using commercial below-knee prosthesis that do not account for lack of shock absorption and stability due to a locked knee 8 tend to engage in motion that may result in changes in loading of the prosthetic feet, in turn causing health challenges.

[0041] Prosthetic knee 2 designs can rely on accurate replication of able-bodied CoP and orientation progression of GRF. Examples of such knees can include locks and latches attached to linkages that move depending on the orientation and location of applied forces and moments. Improper loading at the foot can result in the knee to unlock too early or too late, which can result in a fall or stumble. The deformation of the prosthetic foot under a user's body weight during a step (using reference loading data) can by calculated based on the force asserted by the user's body weight and the resulting ground reaction force (GRF_X, and GRF_y). The prosthetic foot may be optimized based on different frameworks by estimating corresponding trajectories of the user’s limbs. The optimization and structural analysis of the prosthetic foot may be analyzed using a finite element analysis. The algorithm used for the optimization may be a genetic algorithm. Therefore, in one embodiment of the present disclosure, a prosthetic foot for individuals with an above -knee amputation replicates able-bodied loading (CoP and GRF progression) to enable predictable knee mechanism operation.

[0042] The prosthetic foot 10 in above -knee amputees directly impacts the performance of the entire leg. Therefore, above-knee amputees need a prosthetic foot 10 that is configured to provide the shock-absorption and stability that is inherent to knee flexion in able-bodied individuals. Stability may be addressed in the prosthetic leg design by locking the knee, and thereby, preventing buckling of the knee, which can result in the user stumbling or a falling. Shock absorption may be provided by knee springs, shock absorption pylons, and/or a prosthetic foot shaped to absorb the shock. Kinematic motion that can be used to evaluate if sufficient shock-absorption is provided when a user is engaging a prosthetic foot. Further, pelvic obliquity, the angle between the hip centers, may be used to describe the effects of shock absorption.

[0043] FIGS. 3A-3D illustrate one embodiment of a passive prosthetic foot 100 optimized for above -knee amputees. A passive prosthetic foot is a prosthetic foot that does not comprise any external energy source and that cannot move on its own. The prosthetic foot 100 optimized for above-knee amputees may include a generally vertical keel 28 and a generally horizontal length of foot 20. The horizontal length of foot 20 includes a generally horizontal elongated forefoot section 21 attached to the keel 28 anterior to an attachment point 22. The forefoot section 21 includes a toe portion 24 anterior to the attachment point 22 comprising the anterior end of the forefoot section 21. The horizontal length of foot 20 further includes a heel 26 positioned posterior to the attachment point 22. As used herein, the term “generally vertical” includes an angle a between the forefoot section 21 and the keel 28 that is approximately in a range from about 45 degrees to about 75 degrees. Alternatively, the angle a can be defined between the heel 26 and the keel 28 and still have similar degree range. In other words, the keel 28 can be considered generally vertical if it is within approximately 45 degrees of being vertical. In the illustrated embodiment, the angle a can be about 54 degrees. In other instances, the angle a can be defined between the ground and the keel, in which case the angle a can be approximately in a range from about 50 degrees to about 75 degrees, and in the illustrated embodiment it is about 60 degrees. As used herein, the term “generally horizontal” includes an angle [3 between the forefoot section 21 or the toe portion 24 and the ground that is approximately in a range from about 3 degrees to about 10 degrees. In the illustrated embodiment, the angle P is about 5 degrees. Alternatively, the angle can be defined between the forefoot section 21 or the heel 26 and the ground and still have a similar degree range. In other words, any of the forefoot section 21, the toe portion 24, and the heel 26 can be considered generally horizontal if it is within approximately 10 degrees of being horizontal.

[0044] In some embodiments, the heel 26 may be a resilient heel 26, such that the heel 26 may be configured to be flexible or to deform under pressure and provide shock absorption when the heel 26 strikes the ground when used by a user. In other words, the heel 26 is able to change shape and there provide shock absorption when the heel 26 strikes the ground. The heel 26 may be approximately in the range of about 50% to about 90% longer than the toe portion 24. In some embodiments, such as the illustrated embodiment, the heel 26 may be approximately 75% longer than the toe portion 24. In some embodiments, the ratio of the forefoot section 21 to the length of foot 20 may be approximately in the range of about 0.3 to about 0.47. A person skilled in the art will appreciate that these values, along with most if not all values in the present disclosure, are dependent, at least in part, on the size (e.g. , weight, height) of the subject wearing the prosthetic foot 100. The heel 26 may have stiffness approximately in the range of about 5 N/mm to about 18 N/mm, although other stiffness values both less than and greater than this range are possible. In some embodiments, the heel 26 may have a stiffness less than approximately 12 N/mm. The prosthetic foot 100 may comprise materials that are low-cost, have high strain-energy density, are easy to manufacture, and/or are consistent. In some embodiments, the prosthetic foot 100 may be comprised of one or more of nylon 6/6, carbon fiber, fiber glass, spring steel, titanium, plastic, an alloy of metals, a polymer, a composite, a resin, a thermoplastic, laminate, a rubber, an elastomer, a non- viscoelastic material, a viscoelastic material, and/or wood.

[0045] The prosthetic foot 100 can be modeled as a 2-D compliant structure using a compliant mechanism optimization technique that includes a set of determinants for the compliant prosthetic foot. With reference to FIG. 4, the 2-D compliant structure may be a parametric shape 30 described by a wide Bezier curve. The parametric shape 30 includes the keel 28, the forefoot section 21, and the heel 26. A wide Bezier curve is defined by a series of control points 32, 34, 36, 38, 40, 42, 44. Using this methodology, a cubic curve can be defined by the position of four control points, reducing a potentially complex shape to a limited number of design variables. The thickness of the curve is added as a variable by using control circles rather than control points and defining the thickness of the wide Bezier curve as a function of the diameters of these control circles.

[0046] As shown in FIG. 4, three wide Bezier curves may be used to describe this prosthetic foot 100 architecture. The main keel 28 portion of the foot 100 may be modeled as a cubic wide Bezier curve, using more than one parameter based on the intended user's body weight, height, foot size and/or preferred walking activity. For example, the keel 28 of the prosthetic foot 100 may be modeled as a cubic wide Bezier curve using control circles 32, 34, 36, 38, and 42 followed by a linear wide Bezier curve using control circles 38, 40, and 42. The heel 26 of the foot 100 is described by a linear wide Bezier curve using the control circles 38, 42, and 44. This foot 100 architecture includes 7 control circles, each of which are defined by three (3) coefficients (x-position, y-position, and diameter). Of the 21 design coefficients, 12 independent coefficients (Cid, Cix, Cz_y, C d, C3x, Cy_y, Cid, C4x, C4d, Cs , C(,d, and C?d) are used in the shape and size optimization, as the remaining nine (9) coefficients (Cix, Ci_y, C4>, Csx, Csy, Cex, Cdy, C?x, and C?y are set by the user’s characteristics (foot length 48 and residuum length) or coupled to an existing coefficient. Upper and lower bounds are imposed on each of the independent coefficients to constrain the shape and size of the structure to approximately fit within the envelope of a biological foot. Such parametrization can enable a variety of prosthetic foot 100 designs with varying stiffness and geometry for both the keel 28 and the heel 26. This foot 100 architecture describes compliant structures that exhibit both plantarflexion and dorsiflexion during a step. Each one of the resulting foot 100 design is a two-dimensional extruded shape that is easily manufacturable with minimal post-processing, enabling rapid-prototyping, and testing. In some embodiments, the prosthetic foot 100 may be modeled as a 2-D compliant structure described by polynomial interpolation. In some embodiments, the prosthetic foot 100 may be modeled as a 2-D compliant structure described by Lagrange function interpolation.

[0047] The framework provided for herein for the optimization of the design of the prosthetic foot 100 based on above -knee gait is able to provide proper interaction with the prosthetic knee and promote overall mobility of an above-knee amputee. More particularly, a Hip Trajectory Error (HTE) framework can be used to optimize the design of prosthetic feet 100 for above-knee amputees. The HTE framework is an extension of a lower leg trajectory error (LLTE) method used to design prosthetic feet for below-knee amputees as described in U.S. Patent No. 11,607,325, entitled “Shape Optimization for Prosthetic Feet,” the disclosure of which is expressly incorporated by reference herein in its entirety.

[0048] The application of the HTE framework accounts for the lack of early and mid- stance knee flexion in above-knee amputees as discussed earlier. Similar to the LLTE framework, the HTE framework uses predicted biomechanical performance of the prosthetic foot to evaluate how the foot deflects when able-bodied loading is applied to it. The HTE framework is set in a sagittal plane and the prosthetic foot 100 is modeled as a 2-D compliant structure. The trajectory of a hip center of an able-bodied user is used as the target for the optimization. The HTE framework optimizes a prosthetic foot design based on reference loading conditions to replicate target able-bodied hip motion with a fully-extended leg through early and mid- stance and provide an HTE score as shown in Equation 1:

where x^hlP_n and y^hlP_n are the predicted motion of the hip,

and y^hlP„ are the able-bodied reference hip motion, Li_eg is the leg length from floor to hip center, and N is the number of stance frames used for the optimization. Normalized average loading data collected from able-bodied subjects (GRF_X, GRF_y, CoP) can be used to calculate the able-bodied reference hip motion (x^n and y^llipn) that can be used as the target reference motion. Additionally, or alternatively, other values determined, recorded, or otherwise known can be used. The HTE framework accounts for body mass, leg length, ankle height (h) 46, and foot length 48 to be defined for each person to customize the prosthetic foot 100 to their body.

[0049] In some embodiments, the deformation of a given prosthetic foot 100 under a user’s body weight during a step can be calculated and used to estimate a corresponding trajectory of the hip center. HTE is determined by comparing the user’s hip center trajectory 18, shown in FIG. 1, to an able-bodied walker for that given prosthetic foot 100 design. Such replication of the hip motion illustrates whether the above-knee amputee user is receiving enough shock absorption that would otherwise be provided with knee flexion 14 in an able- bodied user. Additionally, the HTE framework allows for the prediction of the performance of the prosthetic foot 100 for above-knee amputees and for better optimization of the prosthetic knee. In one embodiment, one or more Bezier curve coefficient, Lagrange function curve parameters, polynomial interpolation curve parameters, and/or ankle length may comprise the set of determinants that will be optimized in a genetic algorithm to minimize the HTE of the prosthetic foot 100. Therefore, a prosthetic foot 100 that is designed based on an optimized set of determinants obtained by minimizing HTE relative to a target kinematic and/or kinetic data set improves gait performance for users with aboveknee amputation. In some embodiments, the target kinematic and/or kinetic data set may be a physiological data set obtained from the user for whom the prosthetic foot is being designed or from an able-bodied individual. The able-bodied individual may be about the same body size and weight as the subject, or the data of the able-bodied individual may be scaled to adjust for differences in body size and weight compared to the user. In other embodiments, the target kinematic data set may be obtained using simulation, measurement of the user, and/or measurement from a population of individuals and scaling in magnitude the measurements from individual(s) of a different body size and weight. Minimizing the HTE with respect to such target kinematic and/or kinetic data ensures that the hip location of a user of a prosthetic foot 100 closely resembles the hip location of an able-bodied individual.

[0050] FIG. 5 illustrates limb positions of a user with a prosthetic foot 100 in comparison to an able-bodied person. The locked knee stance 14 of the prosthetic foot user shows the position of the knee 8' (as indicated by knee prosthesis 2) and hip 6', while the knee flexion 16 stance of an able-bodied walker shows the position of the knee 8 and hip 6 of an able- bodied person. As illustrated, the position of the knee 8' and hip 6' closely align with the position of the knee 8 and hip 6 of an able-bodied person.

[0051] The optimization of the design of the prosthetic foot 100 based on the HTE framework may be done by implementing finite element analysis. The reference kinetic and kinematic data as well as the chosen material properties maybe entered into a structural analysis algorithm in MATLAB (Mathworks®, Natick, MA), where the deflection of the 2-D prosthetic foot 100 can be calculated using a finite element analysis. Using a built-in genetic algorithm, a population of solutions may be evaluated using the HTE framework objective to obtain HTE scores. The genetic algorithm may be a stochastic algorithm. By way of example, in the present disclosure, version 23.2 of the global optimization algorithm found at the following link from MathWorks® was used in conjunction with the optimization process described herein, and which is incorporated by reference herein in its entirety (both the direct link and any links or sublinks associated therewith): https://www.mathworks.com/products/global-optimization.html. Related documentation and examples of other algorithms that can be used in conjunction with the present disclosure are provided for at the following link, which is incorporated by reference herein in its entirety (both the direct link and any links or sublinks associated therewith): https://www.mathworks.com/help/gads/genetic-algorithm.html. The deflection of the prosthetic foot 100 and the resulting location of the hip center may be calculated for each evaluated frame, or a point in time throughout the stance phase. A typical gait cycle comprises a stance phase and a swing phase. The stance phase is the period of time when a user’ s foot is in contact with the floor. The stance phase comprises the time between heelstrike to toe-off. For example, the stance phase comprises heel-strike, foot-flat, mid-stance, push-off, and toe-off. The evaluated frames may be chosen at different times during the completion of the stance phase, where a 100% of a stance phase indicates the time between a heel-strike and the consecutive toe-off. The evaluated frames may be chosen based on Nyquist frequency analysis, where it may assumed that walking has a frequency of about 2 Hz. The number of frames included in such analysis may range from about six (6) frames to about 100 frames. In some embodiments, the number of frames can be 10 frames, which provides sufficient information while keeping optimization time under two (2) hours per one (1) solution as relying upon 100 frames, for example, can be computationally expensive. For example, in one embodiment, the frames included in the HTE optimization of the prosthetic foot 100 designed based on the Bezier coefficients described earlier may include about 8%, about 15% of the stance phase, about 22% of the stance phase, about 29% of the stance phase, about 36% of the stance phase, about 43% of the stance phase, about 50% of the stance phase, about 57% of the stance phase, about 64% of the stance phase, or about 68% of the stance phase of the stance phase, among other options.

[0052] The determinants that define the prosthetic foot design or shape (e.g. , one or more of the Bezier coefficients) that result in the lowest HTE score, while satisfying the constraints such as maximum stress and a design within a standard foot outline, may be chosen as the optimal solution. Therefore, the optimized set of determinants may not necessarily be the global minima. The prosthetic foot 100 designed by combing the compliant mechanism optimization techniques may result in prosthetic foot design parameters that do not exceed a predefined design space. In some embodiments, the HTE framework may be used to optimize compliant prosthetic feet 100 designed with a different number and/or definition of Bezier Curve coefficients than those described above.

[0053] FIG. 6 compares the simulated performances of LLTE and HTE prosthetic feet design framework for people with an above-knee amputation who do not exhibit early and mid-stance knee flexion. Performance is evaluated in terms of deviation from able-bodied hip motion 50 via the HTE score, where an HTE score closer to zero indicates better performance. In the case of the prosthetic foot optimized under the LLTE framework, the hip center locations were calculated as the extension of the lower leg, assuming that the knee remains unflexed during early and mid-stance for above-knee amputees. In some embodiments, the HTE score for a prosthetic foot optimized under the LLTE framework may be about six (6) times higher than the HTE score for a prosthetic foot optimized under the HTE framework. In other embodiments, the HTE score for a prosthetic foot optimized under the LLTE framework may be about two (2) times to about seven (7) times higher than the HTE score for a prosthetic foot optimized under the HTE framework. Other amounts less than two, between two and seven, and greater than seven are also possible

[0054] In the simulation studies of LLTE and HTE feet, as shown in FIGS. 5A-5C, a prosthetic foot optimized under the HTE framework 54 may provide a closer replication of the user’s hip motion compared to a prosthetic foot optimized under the LLTE framework 52 for above-knee amputees. FIG. 6B illustrates the target reference motion 56 is shown with dashed lines while solid lines 58, 60 represent the LLTE simulated motion and the HTE simulated motion, respectively. As shown in FIG. 6C, the effect of the framework objective function choice (LLTE vs. HTE) on predicted gait is especially visible at the point where able-bodied peak knee flexion during early and mid-stance would typically occur. Prosthetic feet optimized under the LLTE framework are designed with the goal to replicate able- bodied knee location and lower leg orientation. This results in the predicted hip center for above knee amputees, who typically do not display early stance flexion, being substantially anterior compared to the predicted hip motion when using a prosthetic foot optimized under the HTE framework. These results suggest that the prosthetic foot optimized under the HTE framework and designed specifically for above-knee amputee gait would result in significantly better biomechanical performance for people with an above-knee amputation. [0055] In some embodiments, the prosthetic feet 100 designed based on the HTE framework may perform the same or better than daily-use prescribed, tuned prosthetic feet based on error from target able-body kinematic and kinetic data (GRF_X, GRF_y, CoP, x^hip _n and y^hip _n). In some embodiments, the prosthetic feet 100 designed based on the HTE framework may have better stability and shock absorption than a corresponding LLTE prosthetic feet designed based on the error from target able-body kinematic and kinetic data (GRF_X, GRF_y, CoP, x^hipn and y^hip _n). In some embodiments, body kinematics may be recreated instead of loading at the foot based on a comparison between total kinetic (GRF_X, GRF_y, CoP) and kinematic error (x^hip and y^hip). In some embodiments, the prosthetic feet 100 designed based on the HTE framework may better replicate key passive prosthetic knee operation parameters (orientation GRFs in sagittal plane and progression of CoP).

The present disclosure provides for a method of moving by a user having the prosthetic foot 100. The user may move a leg that is amputated above the knee and includes the prosthetic foot in a manner such that the resulting hip motion of the user substantially replicates hip motion of a comparable able-bodied user. The hip motion of the user using the prosthetic foot 100 may be approximately in a range of about 1% to about 25% of the hip motion of the able-bodied user to be considered as substantially replicating hip motion of a comparable able-bodied user. The kinematic error along the x-axis (x^hip) may be approximately in a range of about 1 % of the hip motion of the able-bodied user in the x-axis to about 20% of the hip motion of the able-bodied user in the x-axis. The kinematic error along the y-axis (y^hip) may be approximately in a range of about 1% of the hip motion of the able-bodied user in the y-axis to about 3% of the hip motion of the able-bodied user in the y-axis. The HTE score for a prosthetic foot optimized under the HTE framework may be approximately 0.01 to about 0.025 for masses approximately in the range of about 60 kilograms to about 80 kilograms and heights approximately in a range of about 1.6 meters to about 1.8 meters. In some embodiments, an optimal value can be about 0.025. A person skilled in the art, in view of the present disclosures, will appreciate that other HTE values can be achieved, including those below and above the values provided for herein (thus values less than 0.01 and values greater than 0.025, e.g. 0.030, 0.040, 0.050, 0.1, etc.). Such values can be dependent, at least in part, on the weight and size of the person using the prosthetic foot, among other parameters. [0056] The prosthetic foot 100 may include a generally vertical keel 28 and a generally horizontal length of foot 20. The horizontal length of foot 20 includes a generally horizontal elongated forefoot section 21 attached to the keel 28 at an attachment point 22. The forefoot section 21 may include a toe portion 24 comprising the anterior portion of the forefoot section 2 Ipositioned anterior to the attachment point 22. The horizontal length of foot 20 may further include a heel 26 attached to the forefoot section 21 and positioned posterior to the attachment point 22. The heel 26 may be approximately in a range of about 50 % to about 90% longer than the toe portion 24. In some instances, a length of the forefoot is about 0.09 meters, measured from a distal-most end of a toe to the attachment point 22, and a length of the heel is about 0. 12 meters, measured from the attachment point 22 to a distal- most end of the heel, such that a length of the foot is about 0.21 meters. The relative shape and size of the keel 28, the forefoot section 21, and the heel 26 provide shock absorption when the above-knee amputee is moving.

[0057] In at least some embodiments, a method of moving for a user having a prosthetic foot designed in manners disclosed herein includes the user using a prosthetic foot that is designed to be based on one or more determinants that have been optimized to minimize a hip trajectory error (HTE) relative to a target kinematic and/or kinetic data set. The one or more determinants may include one or more of the Bezier curve coefficients Cid, C_3x, C_3y, C2d, C₃x, C₃y, C₃d, Cdx, Cdd, Csd, Ced, and C? , Cix, Ciy, Cdy, C_5x, Csy, Cdx, Cey, C?x, and C?y as described in reference to FIG. 4. The target kinematic and/or kinetic data set may be a physiological data set obtained from the user for whom the prosthetic foot is being designed or from an able-bodied individual. As described earlier with respect to equation 1 , the HTE is based on predicted hip motion of the above -knee amputee using the prosthetic foot, hip motion of the able-bodied user, leg length from floor to hip center of the above-knee amputee using the prosthetic foot and/or number of stance frames used for optimization.

[0058] Example 1: Validation of able-bodied loading assumption in the above-knee prosthetic design optimization

[0059] The HTE framework may be used to optimize the stiffness of the prosthetic foot to closely replicate able-bodied hip center trajectory. However, it is also important to replicate the able-bodied loading at the foot to validate able-bodied loading assumption in the design optimization. In one embodiment, normalized root mean squared error (NRMSE) is used to measure how well each foot condition replicates the target able-bodied kinematics and kinetics. The NRMSE is calculated for five key variables for each subject: vertical GRF, horizontal GRF in the direction of walking, CoP progression, and hip kinematic deviations in the sagittal plane (x^hip and y^hip). To assess the overall effectiveness of each prosthetic foot condition at enabling replication of the target able-bodied walking trajectory, a total deviation score is derived for each participant by summing up the resulting error for each of the five variables mentioned above. The unlocking and flexing mechanisms are designed to operate based on GRF orientation (angle created by vertical and horizontal GRFs in the sagittal plane) and GRF location according to the CoP.

[0060] To investigate the efficacy of each prosthetic foot condition for use with passive prosthetic knees, the NRMSE is calculated for GRF orientation and CoP progression through stance and a total “knee variables” deviation score is derived by summing the resultant NRMSE for CoP and GRF orientation. For this analysis, only the data points from heel strike to initiation of flexion are analyzed as after unlocking, the knee and the foot start to interact with each other. In able-bodied gait, the initiation of flexion is identified at the minimum knee flexion angle before swing flexion, however, due to the lack of early and mid-stance flexion that method could not be used. For prosthetic knee users, methods to identify the initiation of flexion use either data collected within the knee (torquemeasurements) or using accelerometers. These methods typically require a custom knee or additional instrumentation. Therefore, the initiation of flexion may alternatively be identified as the moment in stance where the knee angular velocity is higher than the 0.1 times the maximum flexion knee angular velocity. This method may be consistent and effective across all subjects and conditions.

[0061] Example 2: Method of designing a prosthetic foot

[0062] The present disclosure provides for some embodiments of a method of designing a compliant prosthetic foot for an above-knee amputee. The method includes using a compliant mechanism optimization technique to identify a parametric curve defined by a set of coefficients for a compliant prosthetic foot as described with respect to FIG. 4. In at least some embodiments, the compliant mechanism optimization technique may include a parameterization step comprising Bezier curve coefficients. The method may include identifying a set of determinants that will be use to minimize a hip trajectory error (HTE). The one or more determinants may be identified by using finite element analysis. In some embodiments, the set of determinants may include one or more of the Bezier curve Coefficients Cid, C2X, C2y, C2d, C3x, C3y, C3d, Cdx, C4d, C5d, C6d, and C₇d, Clx, Cly, Cdy, C₅x, Csy, Cex, Ce_y, C_7x, and C?y as described in reference to FIG. 4. In some embodiments, the set of determinants may include the ankle height of the user (h).

[0063] The method can further include calculating the HTE under reference loading conditions and optimizing the set of determinants by minimizing the HTE relative to a target kinetic and kinematic data. As described earlier, the target kinematic and/or kinetic data set may be a physiological data set obtained from the user for whom the prosthetic foot is being designed or from an able-bodied individual. The target kinematic and/or kinetic data set may be based on body size and weight of the user. In some embodiments, the minimization of the HTE and the optimization of the set of determinants may by constrained by design parameters of the complaint prosthetic foot to not exceed a predefined design space. The design parameters may include, but are not limited to the user’s body weight, height, foot size, and/or preferred walking activity.

[0064] Additionally, the method can include designing the prosthetic foot 100 for the user based on the optimized set of determinants. The method may further include fabricating or manufacturing the prosthetic foot 100 based on the design of the prosthetic foot 100 by employing at least one of machining, three-dimensional printing, implementing a layup method, implementing a waterjet method, additive fabrication, subtractive fabrication, lamination, composite manufacture, injection molding, carbon fiber fabrication, extrusion, casting, molding, co-molding, carving, and/or vulcanization.

[0065] Examples of the present disclosure include:

1. A prosthetic foot for use with an above-knee amputee, comprising: a generally vertical keel; a generally horizontal elongated forefoot section attached to the keel at an attachment point, the forefoot section having a toe portion anterior to the attachment point; and a heel attached to the forefoot section and positioned posterior to the attachment point, wherein the keel, the forefoot section, and the heel are configured to provide for a user who is an above-knee amputee both shock absorption and replication of hip motion of a comparable able-bodied user despite a lack of early-stance knee flexion and mid-stance knee flexion due to the user being an above-knee amputee. 2. The prosthetic foot of example 1, wherein the keel and the forefoot section are configured to be positioned at an angle of about 45 degrees to about 75 degrees with respect to each other.

3. The prosthetic foot of example 1 or 2, wherein the heel is at least 50% longer than the toe portion in length.

4. The prosthetic foot of any of examples 1 to 3, wherein the heel is configured to deform under pressure and provide shock absorption when the heel strikes the ground.

5. The prosthetic foot of any of examples 1 to 4, wherein the prosthetic foot is optimized based on at least one of the user’s body weight, height, foot size, limb length, or walking pattern.

6. The prosthetic foot of example 5, wherein the prosthetic foot is optimized based on at least two of the user’s body weight, height, foot size, limb length, or walking pattern.

7. The prosthetic foot of example 6, wherein the prosthetic foot is optimized based on at least three of the user's body weight, height, foot size, limb length, or walking pattern.

8. The prosthetic foot of any of examples 1 to 7, wherein the keel and the forefoot section are shaped according to a parametric curve characterized by one or more determinants selected from a group including h, Cid, C2x, C y, C2 , ix, Csy, Gi, C4x, C4d, Csd, Ced, and C?d-

9. The prosthetic foot of any of examples 1 to 8, wherein the keel and the forefoot section are shaped to minimize a hip trajectory error (HTE).

10. The prosthetic foot of example 9, wherein determining the HTE comprises calculating an HTE score based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user.

11. The prosthetic foot of example 10, wherein the HTE score is further based on leg length from floor to hip center of the above-knee amputee using the prosthetic foot and number of stance frames used for optimization.

12. The prosthetic foot of example 10 or 11, wherein the HTE score is approximately in the range of about 0.01 to about 0.025. 13. The prosthetic foot of any of examples 1 to 12, wherein the hip motion of the aboveknee amputee using the prosthetic foot is approximately in the range of about 3% to about 20% of the hip motion of the able-bodied user.

14. The prosthetic foot of any of examples 1 to 13, wherein the prosthetic foot comprises at least one of nylon 6/6, carbon fiber, fiber glass, spring steel, titanium, plastic, an alloy of metals, a polymer, a composite, a resin, a thermoplastic, laminate, a rubber, an elastomer, a non- viscoelastic material, a viscoelastic material, or wood.

15. A method of designing a compliant prosthetic foot, comprising: using a compliant mechanism optimization technique that includes a set of determinants for the compliant prosthetic foot; calculating a hip trajectory error (HTE) under at least one reference loading condition; optimizing the set of determinants by minimizing the hip trajectory error relative to a target kinematic data set; and designing the compliant prosthetic foot based on the optimized set of determinants.

16. The method of example 15, wherein the method further comprises fabricating the compliant prosthetic foot based on the optimized set of determinants.

17. The method of example 15 or 16, wherein the prosthetic foot comprises: a generally vertical keel; a generally horizontal elongated forefoot section attached to the keel at an attachment point; and a heel attached to the forefoot section and positioned posterior to the attachment point.

18. The method of any of examples 15 to 17, wherein the set of determinants comprises one or more determinants selected from h, Cid, C2x, C2y, C2d, Csx, C3y, Csd, C4x, C4d, Csd, Ced, and C?d-

19. The method of any of examples 15 to 18, wherein the optimized set of determinants is based on at least one of the user's body weight, height, foot size, limb length, or walking pattern. 20. The method of any of examples 15 to 19, wherein the target kinematic data set includes a physiological data set of a user.

21. The method of example 20, wherein the target kinematic data set is a physiological data set obtained from an able-bodied subject with about the same body size and mass as the user.

22. The method of example 20, wherein the target kinematic data set is a physiological data set scaled from an able-bodied subject to adjust for differences in body size and mass compared to the user.

23. The method of any of examples 15 to 22, wherein calculating the hip trajectory error (HTE) comprises calculating an HTE score based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user.

24. The method of example 23, wherein calculating the HTE score is further based on leg length from floor to hip center of the above-knee amputee using the prosthetic foot and number of stance frames used for optimization.

25. The method of example 23 or 24, wherein the HTE score is approximately in the range of about 0.01 to about 0.025.

26. The method of any of examples 15 to 25, wherein the compliant mechanism optimization technique includes a parameterization step in which wide Bezier curve coefficient are incorporated into a genetic algorithm to determine a set of determinants that minimizes a hip trajectory error of the prosthetic foot.

27. The method of any of examples 15 to 26, wherein the compliant mechanism optimization technique includes a parameterization step in which polynomial interpolation curve parameters are incorporated into a genetic algorithm to determine a set of determinants that minimizes a hip trajectory error of the prosthetic foot.

28. The method of any of examples 15 to 27, wherein the compliant mechanism optimization technique includes a parameterization step in which Lagrange function curve parameters are incorporated into a genetic algorithm to determine a set of determinants that minimizes a hip trajectory error of the prosthetic foot. 29. The method of any of examples 15 to 28, further comprising combining the compliant mechanism optimization technique with the hip trajectory error and identifying prosthetic foot design parameters that do not exceed a predefined design space.

30. The method of any of examples 15 to 29, wherein the prosthetic foot is fabricated by at least one of machining, three-dimensional printing, implementing a layup method, implementing a waterjet method, additive fabrication, subtractive fabrication, lamination, composite manufacture, injection molding, carbon fiber fabrication, extrusion, casting, molding, co-molding, carving, or vulcanization.

31. A method of moving by an above-knee amputee having a prosthetic foot, comprising: moving a leg that is amputated above the knee and includes a prosthetic foot in a manner such that resulting hip motion of the above-knee amputee substantially replicates hip motion of a comparable able-bodied user.

32. The method of example 31, wherein the hip motion of the above-knee amputee using the prosthetic foot is approximately in a range of about 3% of the hip motion of the able- bodied user to about 20% of the hip motion of the able-bodied user.

33. The method of example 32, wherein the prosthetic foot comprises: a generally vertical keel; a generally horizontal elongated forefoot section attached to the keel at an attachment point, the forefoot section having a toe portion anterior to the attachment point; and a heel attached to the forefoot section and positioned posterior to the attachment point, and wherein the keel, the forefoot section, and the heel provide shock absorption when the above-knee amputee is moving.

34. The method of example 32 or 33, wherein the prosthetic foot is designed based on one or more determinants optimized to minimize a hip trajectory error (HTE) relative to a target kinematic data set.

35. The method of example 34, wherein the HTE is based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user. 36. The method of example 35, wherein the HTE is further based on leg length from floor to hip center of the above-knee amputee using the prosthetic foot and number of stance frames used for optimization.

[0066] One skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

Claims

CLAIMS What is claimed is:

1. A prosthetic foot for use with an above-knee amputee, comprising: a generally vertical keel; a generally horizontal elongated forefoot section attached to the keel at an attachment point, the forefoot section having a toe portion anterior to the attachment point; and a heel attached to the forefoot section and positioned posterior to the attachment point, wherein the keel, the forefoot section, and the heel are configured to provide for a user who is an above-knee amputee both shock absorption and replication of hip motion of a comparable able-bodied user despite a lack of early-stance knee flexion and mid-stance knee flexion due to the user being an above-knee amputee.

2. The prosthetic foot of claim 1, wherein the keel and the forefoot section are configured to be positioned at an angle of about 45 degrees to about 75 degrees with respect to each other.

3. The prosthetic foot of claim 1, wherein the heel is at least 50% longer than the toe portion in length.

4. The prosthetic foot of claim 1, wherein the heel is configured to deform under pressure and provide shock absorption when the heel strikes the ground.

5. The prosthetic foot of claim 1, wherein the prosthetic foot is optimized based on at least one of the user’s body weight, height, foot size, limb length, or walking pattern.

6. The prosthetic foot of claim 1, wherein the keel and the forefoot section are shaped according to a parametric curve characterized by one or more determinants selected from a group including h, Cid, Cax, Cay, Cad, Ca_x, Ca_y, Cad, C4x, C4d, Csd, Cea, and C?d-

7. The prosthetic foot of claim 1, wherein the keel and the forefoot section are shaped to minimize a hip trajectory error (HTE).

8. The prosthetic foot of claim 7, wherein determining the HTE comprises calculating an HTE score based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user.

9. The prosthetic foot of claim 1, wherein the hip motion of the above-knee amputee using the prosthetic foot is approximately in the range of about 3% to about 20% of the hip motion of the able-bodied user.

10. A method of designing a compliant prosthetic foot, comprising: using a compliant mechanism optimization technique that includes a set of determinants for the compliant prosthetic foot; calculating a hip trajectory error (HTE) under at least one reference loading condition; optimizing the set of determinants by minimizing the hip trajectory error relative to a target kinematic data set; and designing the compliant prosthetic foot based on the optimized set of determinants.

11. The method of claim 10, wherein the method further comprises fabricating the compliant prosthetic foot based on the optimized set of determinants.

12. The method of claim 10, wherein the prosthetic foot comprises: a generally vertical keel; a generally horizontal elongated forefoot section attached to the keel at an attachment point; and a heel attached to the forefoot section and positioned posterior to the attachment point.

13. The method of claim 10, wherein the set of determinants comprises one or more determinants selected from h, Cid, C2x, Cyy, C2d, C3x, C3_y, C3d, C4x, C4d, Od, Ced, and C?d.

14. The method of claim 10, wherein the optimized set of determinants is based on at least one of the user's body weight, height, foot size, limb length, or walking pattern.

15. The method of claim 10, wherein the target kinematic data set includes a physiological data set of a user.

16. The method of claim 10, wherein calculating the hip trajectory error (HTE) comprises calculating an HTE score based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user.

17. A method of moving by an above-knee amputee having a prosthetic foot, comprising: moving a leg that is amputated above the knee and includes a prosthetic foot in a manner such that resulting hip motion of the above-knee amputee substantially replicates hip motion of a comparable able-bodied user.

18. The method of claim 17, wherein the hip motion of the above-knee amputee using the prosthetic foot is approximately in a range of about 3% of the hip motion of the able-bodied user to about 20% of the hip motion of the able-bodied user.

19. The method of claim 18, wherein the prosthetic foot comprises: a generally vertical keel; a generally horizontal elongated forefoot section attached to the keel at an attachment point, the forefoot section having a toe portion anterior to the attachment point; and a heel attached to the forefoot section and positioned posterior to the attachment point, and wherein the keel, the forefoot section, and the heel provide shock absorption when the above-knee amputee is moving.

20. The method of claim 19, wherein the HTE is based on predicted hip motion of the above-knee amputee using the prosthetic foot and hip motion of the able-bodied user.